`make install` doesn't handle non-existent binary dir

[aozgaa]

What happened?
make install tries to elevate at the install(1) subcommand If the PREFIX/DESTDIR doesn't exist, then fails anyways:

    @if [ -w "$(PREFIX)/bin" ]; then \
      install .build/release/$(BINARY) $(PREFIX)/bin/$(BINARY); \
    else \
      sudo install .build/release/$(BINARY) $(PREFIX)/bin/$(BINARY); \
    fi

From test(1):

    -w file       True if file exists and is writable.  True indicates only that the write flag is on.  The file is not writable on a read-only file system even if this test indicates true.

What did you expect?

I'd expect that the install rule either creates the dest dir using inherited permissions, or fails without trying to install/proceed further. In any case, the alternative convention chosen should be documented.

Conventionally, elevating would be taken of by running make itself elevated, something like

make build && sudo make install

But see #83 for why this isn't currently practical.

Steps to reproduce

1. Case 1 -- PREFIX doesn't exist leads to spurious elevation, then failure anyways

% make install PREFIX=${HOME}/.does_not_exist  
0.9.20 → 0.9.21
swift build -c release
[1/1] Planning build
Building for production...
[5/5] Linking apfel
Build complete! (9.95s)
install: /Users/art/.does_not_exist/bin/INS@ogM8iL: No such file or directory
make: *** [install] Error 71

2. Case 2 -- bin dir doesn't exist leads to spurious elevation, then failure anyways
   % mkdir -p ~/.does_exist
   % make install PREFIX=${HOME}/.does_exist
   0.9.21 → 0.9.22
   swift build -c release
   [1/1] Planning build
   Building for production...
   [5/5] Linking apfel
   Build complete! (9.43s)
   install: /Users/art/.does_exist/bin/INS@ZA8LZD: No such file or directory
   make: *** [install] Error 71

3) Case 3 -- bin dir exists leads user or admin install based on writeability:

% mkdir -p ~/.does_exist/bin
% make install PREFIX=${HOME}/.does_exist
0.9.22 → 0.9.23
swift build -c release
Building for production...
[5/5] Linking apfel
Build complete! (4.31s)
✓ installed: apfel v0.9.23

**Environment**
- macOS version: (`sw_vers`)

% sw_vers
ProductName: macOS
ProductVersion: 26.4
BuildVersion: 25E246

- apfel version: (`apfel --version`)

% apfel --version
apfel v0.9.22
% git log -1
commit 07b177f (tag: v0.9.18, origin/main, origin/HEAD, main)
Author: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Date: Sun Apr 12 11:37:02 2026 +0000

release v0.9.18

- Install method: built from source
- `apfel --model-info` output: N/A

[Arthur-Ficial]

Thanks for the report -- confirmed and fixed on main.

Two changes in the Makefile:

1. make install now creates $(PREFIX)/bin if it doesn't exist (with appropriate permissions), so all three of your cases work correctly.

2. Bonus: generate-build-info no longer overwrites Sources/BuildInfo.swift when nothing changed. Previously it wrote a new timestamp on every build, which invalidated Swift's build cache and forced a recompile+relink even with zero source changes. Now it uses the git commit date (stable) and only touches the file when content actually differs. Consecutive make build calls are true no-ops (~0.2s).

To try it:

git pull origin main
make install PREFIX=$HOME/.local  # works even if ~/.local/bin doesn't exist yet

Leaving the issue open until you confirm it works for you.

[Arthur-Ficial]

Verified fixed on main. Ran your three reproduction cases locally against v1.0.3:

Case 1: PREFIX does not exist      → ✓ installed
Case 2: PREFIX exists, bin doesn't → ✓ installed
Case 3: bin exists                 → ✓ installed

The Makefile now creates $(PREFIX)/bin when missing (with appropriate elevation) before running install. The fix has been in main since v1.0.0 and shipped in v1.0.1-v1.0.3.

brew upgrade apfel to get it on the brew channel, or git pull && make install if you build from source.

Thanks again for the clear, reproducible report — closing this one out.